This paper provides an overview of the issues surrounding the design and choice of appropriate missions for a new class of unmanned flying vehicles known as MicroFlyers, Micro Air Vehicles, and Aerial Robots. These terms are often used interchangeably to refer to small flying machines varying from what amounts to "intelligent dust" up to vehicles in the size range of small radio-controlled models (i.e,, having a typical maximum dimension of one meter). Because of the size of this class of air vehicle, it can engage in missions that are non- traditional, such as indoor flight through confined spaces, or en mass, to overwhelm a target in swarms. Also because of size, many of these vehicles will have to be autonomous. In some cases, the design of the vehicle will benefit from biological mimicry wherein the behavioral and locomotive techniques used by birds and insects will be of advantage. However, the small size of these air vehicles will also constrain then in the physical environment in much the same way that insects are not necessarily free to navigate at will in the presence of wind and precipitation.